Shape-fit glenoid reaming systems and methods

ABSTRACT

Disclosed herein are systems and methods for securing a glenoid baseplate to a resected glenoid cavity in a preoperatively planned position. Image information obtained from the glenoid cavity and surrounding scapula is analyzed to determine the location of optimal bone stock. A guide is designed based on the image information, the guide having a patient specific contact surface that contacts a surface of the bone in a preoperatively planned position. The guide is designed to have a cannulated portion including a specific length. A marking pin having at least one reference feature is drilled into the glenoid cavity. The length of the cannulated portion of the guide is based on a location of the at least one reference feature on an outer surface of the marking pin. A cannulated reamer guided by the marking pin is then used to resect the glenoid cavity until a stop surface of the cannulated reamer contacts an end of the marking pin.

FIELD OF THE INVENTION

The present invention relates to the use of patient-specific guides inshoulder arthroplasty procedures, and in particular relates to the useof first and second patient-specific guides during such procedures toensure that components of a shoulder arthroplasty system are fixatedwith respect to bone in a preoperatively planned position andorientation.

BACKGROUND OF THE INVENTION

Joint replacement procedures are used to repair damaged joints. During ajoint replacement procedure the joint is preferably aligned, bone orbones of the joint may be resected, and a prosthesis may be implanted onthe resected bone. Joint replacement procedures may be performed on theknee, hip, shoulder or elbow joints, for example. Accuracy of jointalignment and bone resection is crucial in a joint replacementprocedure. A small misalignment may result in soft tissue or ligamentimbalance and consequent failure of the joint replacement procedure.Provision of patient specific or customized cutting guides andprostheses has been used to attempt to improve the outcome of jointreplacement procedures.

Preoperative planning is used to prepare a surgical plan based on thescan data or to determine what instruments or prosthetic componentsshould be used to achieve a desired surgical result. Preoperativeplanning is also used to design such patient-specific guides andprostheses for use in joint replacement procedures. Prior to thesurgical procedure, scan data associated with a joint of the patient isgenerally obtained, a three-dimensional model of the joint based on thescan data is prepared, and guides and/or prostheses based on the modelare designed. Once the guides and/or prostheses are designed,information regarding manufacture of these components may be sent toadditive manufacturing equipment for manufacture, for example.

Patient-specific guides generally include an inner guide surfacedesigned to mate with a joint surface of the patient such that the guideand joint surface are in a nesting relationship to one another.Accordingly, such guides may mate or “lock” onto the articular surfaceof the joint in a unique position determined in a final surgical plan.Apertures in the guide are generally designed to locate a guide memberor guide a resection device. The guides are preferably designed withsuch apertures in a preoperatively planned position in order to achievea desired bone resection such that a prosthesis can be placed in adesired position and orientation.

In tradition and reverse shoulder arthroplasty procedures it isimportant to accurately locate a prosthesis for attachment to thescapula. In these procedures, fixation screws are used to secure aglenoid cup or baseplate for glenosphere, for example, to the scapula.In order for the cup or baseplate to be sufficiently secured to endureloads during physical therapy and use post surgery, the fixation screwsgenerally need to be fixated to healthy bone stock. There exists a needfor locating these prostheses along with fixation screws thereof in apreoperatively planned position and orientation with respect to thenative bone stock.

BRIEF SUMMARY OF THE INVENTION

A first aspect of the present invention is a method for attaching abaseplate to a glenoid in a shoulder arthroplasty procedure. The methodincludes scanning the patient anatomy, namely the shoulder jointincluding at least the glenoid and scapula. The scan is analyzed todetermine optimal prosthesis placement and fixation based on availablebone stock. After analyzing prosthesis placement and fixation, first andsecond guides are designed to ensure that such placement and fixation isreproducible intraoperatively. The first guide is configured to directlyinterface with the bone for optimal baseplate placement and the secondguide directly interfaces with the baseplate for optimal screw fixation.

The method may include contacting the glenoid with a first guide havinga central borehole and a first reference marker and placing a pilot wirethrough the central borehole and into the glenoid. Further, the methodmay include orienting the baseplate with respect to the glenoid byinserting the pilot wire through a central screw hole of the baseplateand aligning a marker on the baseplate with respect to the firstreference marker of the first guide and then attaching a second guide tothe baseplate such that at least one borehole of the second guide isaligned to at least one peripheral screw hole of the baseplate.

A second aspect of the present invention is a method of attaching abaseplate to a glenoid in a shoulder arthroplasty procedure comprisingusing a first guide to create a first reference and a second referencewith respect to the glenoid, orienting the baseplate with respect to theglenoid using the first and second references, fixing the baseplate tothe glenoid with a central screw, and attaching a second guide to thebaseplate such that at least one borehole of the second guide is alignedto at least one peripheral screw hole of the baseplate.

In one embodiment of this second aspect, the first guide has a patientspecific contact surface that contacts the glenoid such that the firstguide engages the glenoid in a preoperatively planned position. Thepatient specific contact surface of the first guide is preferablycreated using image information obtained from scanning the glenoid.

In another embodiment of this second aspect, the method furthercomprises creating the first reference by inserting a pilot wire througha central borehole in the first guide and at least partially into theglenoid and creating the second reference by marking the glenoid using afirst reference marker on the first guide. The second reference mark maybe a notch located on an outer periphery of the first guide.

In yet another embodiment of this second aspect, the central borehole ofthe first guide includes a central axis having a first trajectory withrespect to the glenoid when the first guide is engaged to the glenoid.

In still yet another embodiment of this second aspect, orienting thebaseplate with respect to the glenoid using the second referenceincludes aligning a marker on the baseplate with respect to the notch ofthe first guide by rotating the baseplate until the marker of thebaseplate is adjacent the notch of the first guide.

In still yet another embodiment of this second aspect, the baseplateincludes four peripheral screw holes and the second guide includes fourboreholes, wherein attaching the second guide to the baseplate includesaligning each of the four boreholes of the second guide to one of thefour peripheral screw holes of the baseplate. Each of the four boreholesof the second guide and each of the four peripheral screw holespreferably includes a trajectory and the trajectories of at least one offour boreholes and at least one of the four corresponding peripheralscrew holes is not coaxial with one another.

Third aspect of the present invention is a method of orientingperipheral screws through peripheral screws holes of a baseplate andinto a glenoid comprising scanning the glenoid to determine desirablebone stock thereof, determining a first angle a first peripheral screwshould be inserted through a first peripheral screw hole of thebaseplate and into glenoid when the baseplate is engaged to the glenoidin a desired position and orientation, using a first guide to create afirst reference and a second references with respect to the glenoid,orienting the baseplate with respect to the glenoid using the first andsecond references, attaching a second guide to the baseplate such thatat least one peripheral screw hole of the second guide is aligned to atleast one peripheral screw hole of the baseplate, and fixing thebaseplate to the glenoid with at least one peripheral screw insertedthrough the at least one peripheral screw hole of the second guide andthe at least one peripheral screw hole of the baseplate and into theglenoid.

In one embodiment of this third aspect, the at least one peripheralscrew hole of the second guide and the baseplate have a centrallongitudinal axis and when the at least one peripheral screw hole of thesecond guide is aligned to at least one peripheral screw hole of thebaseplate, the central longitudinal axes are angled with respect to oneanother.

In yet another embodiment of this third aspect, the first reference iscreated by inserting a pilot wire through a central borehole in thefirst guide and at least partially into the glenoid and the secondreference is created by marking the glenoid using a first referencemarker on the first guide. The second reference marker is preferably anotch located on an outer periphery of the first guide.

In still yet another embodiment of this third aspect, the centralborehole of the first guide includes a central axis having a firsttrajectory with respect to the glenoid when the first guide is engagedto the glenoid.

In still yet another embodiment of this third aspect, orienting thebaseplate with respect to the glenoid using the second referenceincludes aligning a marker on the baseplate with respect to the notch ofthe first guide by rotating the baseplate until the marker of thebaseplate is adjacent the notch of the first guide.

A fourth aspect of the present invention is a system for resecting apreoperatively planned depth into bone comprising a guide having apatient specific contact surface that contacts a surface of the bone ina preoperatively planned position, the guide having a cannulated portionincluding a length; and a marking pin having first and second ends, thefirst end adapted to be drilled into the bone, the marking pin having atleast one reference feature on an outer surface thereof, wherein thelength of the cannulated portion of the guide is based on a location ofthe at least one reference feature on the outer surface of the markingpin.

A fifth aspect of the present invention is a method of resecting apreoperatively planned depth into bone comprising contacting a surfaceof the bone in a preoperatively planned position with a guide having apatient specific contact surface, the guide having a cannulated portionincluding a length; inserting a first end of a marking pin into thecannulated portion of the guide and into contact with the surface of thebone, the marking pin having at least one reference feature on an outersurface thereof; and drilling at least a portion of the marking pin intothe bone until the at least one reference feature on the outer surfaceof the marking pin lies adjacent a receiving end of the cannulatedportion of the guide.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be better understood on reading the followingdetailed description of non-limiting embodiments thereof, and onexamining the accompanying drawings, in which:

FIG. 1 is an anterior view of general shoulder anatomy.

FIG. 2 is a lateral view of one embodiment of a surgical approach to theglenoid.

FIG. 3A is a perspective view of one embodiment of a patient-specificguide for engaging an unresected glenoid.

FIG. 3B is a side cross-sectional plan view of the guide shown in FIG.3A taken along line 3B-3B.

FIG. 4A is a front plan view of one embodiment of a glenoid baseplatefor engaging a resected glenoid.

FIG. 4B is a side cross-sectional plan view of the baseplate shown inFIG. 4A.

FIG. 4C is a detail view of a central screw hole of the baseplate shownin FIG. 4B taken along line 4B-4B.

FIG. 4D is a detail view of a peripheral screw hole of the baseplateshown in FIG. 4B taken along line 4B-4B.

FIG. 4E is a central screw coupled to a central screw hole of thebaseplate shown in FIG. 4B.

FIG. 5A is a front plan view one embodiment of a patient-specific guidefor engaging a glenoid baseplate.

FIG. 5B is a side cross-sectional plan view of the guide shown in FIG.5A taken along line 5B-5B.

FIG. 6 is a flowchart of one embodiment of a method of the presentinvention.

FIG. 7A is an anterior view of the scapula of one embodiment of apatient-specific guide used in marking the glenoid for locating aglenoid baseplate in a preoperatively planned position and orientation.

FIG. 7B is a lateral view of the guide shown in FIG. 7B engaged to theglenoid.

FIG. 8A is one embodiment of a guidewire gauge for guiding reaming depthof a glenoid.

FIG. 8B is one embodiment of the guidewire gauge shown in FIG. 8Acoupled to a guide engaged to the glenoid in which an end of theguidewire gauge is located a desired distance into the glenoid cavity.

FIG. 8C is one embodiment of the guidewire gauge shown in FIG. 8Acoupled to another embodiment of a guide engaged to the glenoid in whichan end of the guidewire gauge is located a desired distance into theglenoid cavity.

FIG. 8D is an exploded view of the scapula of FIG. 7A with a guidewiregauge located in a marked position and a cannulated instrument forpreparing the glenoid.

FIG. 8E shows one embodiment of a cannulated instrument coupled to theguidewire gauge of FIG. 8A.

FIG. 9 depicts the scapula of FIG. 3 with one embodiment of a glenoidbaseplate secured thereto via a central screw.

FIG. 10 depicts a patient-specific guide engaged to the glenoidbaseplate of FIG. 9B guiding peripheral screws into the baseplate andinto the resected glenoid at a preoperatively planned trajectory.

FIG. 11A is a partial cross-sectional plan view of one embodiment of apatient-specific guide engaged to native bone of a glenoid cavity andscapular bone.

FIG. 11B is a plan view of another embodiment of a guidewire gauge ormarking pin of the present invention.

FIG. 11C is a perspective exploded view of a cannulated reamer having ashaft portion and a reamer portion.

FIG. 11D is a cross-sectional view of the cannulated reamer portionsshown in FIG. 11C.

FIG. 12A is a partial cross-sectional plan view of one embodiment of theguidewire gauge shown in FIG. 11B at least partially housed within thepatient-specific guide shown in FIG. 11A and engaged to native bone ofthe glenoid cavity and scapular bone.

FIG. 12B is a partial cross-sectional view of the guidewire gauge shownin FIG. 12A with the patient-specific guide having been removed.

FIG. 12C is a plan view of the guidewire gauge shown in FIG. 12B atleast partially housed within the cannulated reamer of FIG. 11C.

FIG. 12D is a plan view of the guidewire gauge shown in FIG. 12B fullyseated within the cannulated reamer of FIG. 11C.

FIG. 13A is plan view of another embodiment of a patient-specific guideengaged to native bone of a glenoid cavity and scapular bone.

FIG. 13B is a perspective view of the patient-specific guide shown inFIG. 13A.

FIG. 13C is a cross-sectional plan view of the patient-specific guideshown in FIG. 13B taken along line 13B-13B.

FIG. 13D is a plan view of cannulated portions of four patient-specificguides each having a different length.

FIG. 14A is an exploded perspective view of one embodiment of guidewiregauge and a cannulated portion of a patient-specific guide.

FIG. 14B is partial cross-sectional view of a portion of a guidewiregauge housed within a cannulated portion of one embodiment of apatient-specific guide having grasping features on an inner surface ofthe cannulated portion.

FIG. 15A is a partial cross-sectional plan view of one embodiment of aguidewire gauge with an embodiment of a patient-specific guide inphantom lines wherein a distance MD1 is measured from an end of theguidewire gauge to an end of a desired resection in the glenoid cavity.

FIG. 15B is a partial cross-sectional plan view of the guidewire gaugeshown in FIG. 15B fully seated within a cannulated reamer shown adistance RD1 measured from an end of the cannulation of the cannulatedreamer to an apex surface of the reamer portion.

FIG. 16 is a plan view of another embodiment of a marking pin orguidewire gauge.

DETAILED DESCRIPTION

As used herein, when referring to bones or other parts of the body, theterm “proximal” means closer to the heart and the term “distal” meansmore distant from the heart. The term “inferior” means toward the feetand the term “superior” means towards the head. The term “anterior”means towards the front part of the body or the face and the term“posterior” means towards the back of the body. The term “medial” meanstoward the midline of the body and the term “lateral” means away fromthe midline of the body.

FIG. 1 is an anterior view of shoulder anatomy, including a scapula 2,clavicle 4, humerus 6, and glenoid 8. FIG. 2 is a lateral view of asurgical approach to glenoid 8 in which a surgical retractor 10 is shownmoving soft tissues from the surgical site to expose glenoid 8. Inshoulder arthroplasty procedure it is essential that a glenoid baseplatebe positioned accurately on a glenoid prior to coupling the baseplate toother components of a shoulders system such as a glenosphere and humeralstem, for example. The present invention includes preoperativelyplanning the position and orientation of central and peripheral screwsthat are used to fix a baseplate 200 with respect to a glenoid 8 in ashoulder arthroplasty procedure by analyzing available bone stock. Afirst patient-specific guide 100 is designed to directly interface withglenoid 8 for optimal baseplate 200 placement and a secondpatient-specific guide 300 is designed to directly interface withbaseplate 200 for optimal peripheral screw fixation.

First guide 100 shown in FIGS. 3A and 3B includes an outer surface 110,a patient-specific inner contact surface 120, and a side surface 130located between outer and inner surfaces 110, 120. First guide 100includes a central borehole 140 therethrough. Central borehole 140 maybe considered as a first reference means as it is used to mark theglenoid in a preoperatively planned position and trajectory. First guide100 may further include a second borehole 150 therethrough, a notch 160located as a recess in side surface 130, and/or a mechanical or visualindicator 160 on or in guide 100. Each of second borehole 150, notch160, and indicator 170 may be considered as a second reference meansused to further mark the glenoid to aid in placement of glenoidbaseplate 200 in a preoperatively planned position and orientation. Eachof these second reference features may be used to mark the glenoid forrotational alignment of glenoid baseplate 200.

Patient-specific inner contact surface 120 of first guide 100 isdesigned to contact glenoid 8 in a preoperatively planned position.Design of the guide includes scanning the shoulder joint using magneticresonance imaging (“MRI”) or computed tomography (“CT”), for example. Avirtual model 8 of glenoid may be created such that it may be shown on agraphics user interface (“GUI”) such as a computer screen. Contactsurface 120 is designed as a negative of at least a portion of glenoid 8and may include an anatomic reference feature 122 such that the firstguide 100 may be dialed into its preoperatively planned position. Thepurpose of dialing in a patient-specific guide such a first guide 100 isthat the guide is stably oriented with respect to the surface that it isdesigned to contact in all six degrees of freedom. Design of anatomicreference features, such as feature 122 in guide 100 for aiding inproper patient-specific guide orientation with respect to a jointsurface it is designed to engage is disclosed, for example, in U.S. Pat.Pub. No. 2011/0313424 titled “Patient-Specific Total Hip Arthroplasty,”the disclosure of which is incorporated by reference herein in itsentirety.

Baseplate 200 is shown in FIGS. 4A-D and includes an outer surface 210,an inner contact surface 220, and a side surface 230 located betweenouter and inner surfaces 210, 220. Baseplate 200 includes a centralborehole 240 and a plurality of lateral boreholes 260 therethrough.Lateral boreholes 260 are located adjacent a periphery of baseplate 200defining side surface 130. FIGS. 4C and 4D are detail views of thestructure of central borehole 240 and a lateral borehole 260,respectively. As shown in these figures, inner contact surface 220 isgenerally parallel to outer surface 210 adjacent to central borehole 240while inner contact surface 220 is angled with respect to outer contact210 adjacent lateral borehole 260. An example of baseplate 200 includingborehole 240 and lateral boreholes 260 is disclosed in U.S. Pat. Pub.No. 2013/0150973 titled “Reverse Shoulder Baseplate with Alignment Guidefor Glenosphere,” the disclosure of which is incorporated by referenceherein in its entirety.

A central screw 280 as shown in FIG. 4E is received in the centralborehole 240 of baseplate 200 such that a head 281 of screw 280protrudes outwardly from outer surface 210 of baseplate 200. The presentinvention may include various embodiments of a central screw having athreaded shaft 282 and a threaded neck 284, which can generate acompression force along the length of the screw when inserted into abone. Central screw 280 of the present invention may create a firstcompression rate when a shaft and a distal end of the screw are engagedwith scapula bone, for example, and a second compression rate when theshaft and a proximal end of the screw are engaged with scapula bone. Thesecond compression rate may be less than the first compression rate, forexample. Such central screws are shown and described in U.S. Ser. No.13/803,615, titled “Compression Screw With Variable Pitch Thread,” filedMar. 14, 2013, the disclosure of which is hereby incorporated byreferences herein in its entirety.

Second patient-specific guide 300 shown in FIGS. 5A and 5B includes anouter surface 310, an inner contact surface 320, and a side surface 330located between outer and inner surfaces 310, 320. Guide 300 includes acentral recess 340 located in inner contact surface 320 for receivinghead 281 of screw 280 protruding outwardly from outer surface 210 ofbaseplate 200. Guide 300 further includes a plurality of lateral orperipheral boreholes 360. Lateral boreholes 360 are located adjacent aperiphery of baseplate 200 defining side surface 330. Each of lateralboreholes 360 defines a trajectory defined by an angle between a centralaxis 370 thereof and inner contact surface 320. Each of lateralboreholes 360 may include a unique trajectory. For example, a firstlateral borehole 360 may have a trajectory of 60° while a second lateralborehole 75°. Guide 300 preferably has four lateral boreholes 360 eachwith a unique optimal trajectory based on preoperative scans taken ofthe patient's scapula. The trajectories are designed such that whenguide 300 is coupled to baseplate 200, the boreholes 260 guideperipheral screws into the lateral boreholes 260 of baseplate 200 andinto the glenoid cavity and surrounding scapula at a predefinedtrajectory based on optimal bone stock. Guide 300 may further include amechanical or visual indicator 370 used as a reference feature forensuring accurate coupling of guide 300 to baseplate 200 includingaccurate rotational alignment of guide 300 with respect to baseplate200.

One method of the present invention includes preparing the glenoid bytargeting the center of the glenoid using a first patient-specific guidehaving a centering guide hole is used to drill a centering hole. Aguide-wire or guide pin is placed into the centering hole and acannulated reamer is placed over the guidewire to guide reaming of theglenoid face progressively until subchondral bone is thoroughly exposed.A glenoid baseplate is attached to the reamed glenoid face in a desiredlocation. A second patient-specific guide having a plurality of lateralboreholes each having a designed trajectory is attached to the glenoidbaseplate. The lateral boreholes are used to guide the trajectory ofperipheral screws through the baseplate and into the prepared glenoid.

FIG. 6 is a flowchart of one embodiment of a method of the presentinvention. In a first step 400 a patient's anatomy is scanned preferablyincluding the glenoid cavity and surround scapula. In step 410, based onthe image information obtained from the scan of the patient's anatomy,first and second patient-specific guides are designed. The design of thefirst and second guides takes into account the structure of a glenoidbaseplate, namely the outer and inner surfaces and thickness thereof aswell as the location and orientation of central and peripheral screwholes thereof. In designing the guides, models of the glenoid baseplateand patient anatomy may be made and shown on a GUI such that a designercan design the first and second guides appropriately. Based on a desiredlocation and orientation of the baseplate with respect to the resectedglenoid, the patient-specific contact surfaces as well as the locationand orientation of reference markers and central and peripheralboreholes can be designed. After the first and second guides aredesigned, each is manufactured for use intraoperatively.

In a subsequent step 420, the first patient-specific guide is placed ina preoperatively planned position on the unresected glenoid. In asubsequent step 430, a guidewire is inserted through a central boreholeof the first guide and into the bone of the glenoid. The guidewire maybe a guidewire gauge having reference markings to indicate the depth theguidewire gauge has been inserted into the glenoid and preferably intocortical bone. In a subsequent step 440, a reference guide is used tomark the glenoid for later baseplate insertion. In a further step 450,the first guide is removed and in step 460, the glenoid is reamed to adesired depth using the guidewire gauge. In a further step 470, theguidewire gauge is removed and in step 480 the baseplate is oriented offof previous reference mark or identifier made in previous step 440. Inyet a subsequent step 490, a central screw is inserted through a centralscrew hole of the baseplate and into the resected glenoid to initiallyfix the baseplate with respect to the resected glenoid. In yet still asubsequent step 500, a second patient-specific guide is coupled to thebaseplate and oriented such that peripheral boreholes of the secondguide are aligned in a preoperatively planned position with respect toperipheral screw holes of the baseplate. Once the peripheral boreholesof the second guide are aligned with the peripheral screw holes of thebaseplate, in step 510 peripheral screw holes are drilled through thebaseplate and into the resected glenoid. In a subsequent step 520, thesecond guide may be removed and in step 530 peripheral screws areinserted into the peripheral screw holes of the baseplate in atrajectory the peripheral screw holes were drilled using the secondguide in step 510.

FIGS. 7A and 7B refer to steps 420-450 described above. FIG. 7A is ananterior view of the scapula of one embodiment of first patient-specificguide 100 used in marking the glenoid for locating a glenoid baseplatein a preoperatively planned position and orientation with FIG. 7Bshowing a lateral view of guide 100 engaged to the glenoid. The firstguide 100 has at least two functions, namely fixing the location forpilot wire insertion and acting as a marker to orient baseplate 200.With respect to the first function, the geometry of guide 100 ensuresthat it can only be placed on the glenoid of the patient in oneorientation. Because the guide has a patient-specific contact surface120, the guide 100 can be dialed in until it is oriented in thepreoperatively planned orientation. Once the guide is placed in itsproper orientation, the surgeon may insert a guidewire through guidehole 140 and into the bone. With respect to the second function, oncethe guidewire is inserted, the surgeon will preferably use a uniqueidentifier or indicator 170 on guide 100 to note which direction issuperior. This may be achieved with a surgical pen to mark orientation,a tab that points to native anatomy, or by any other unique identifier,for example. This marker will later be aligned with a feature 270 onbaseplate 200 to ensure baseplate 200 is oriented in a preoperativelyplanned orientation.

FIGS. 8A-8E refer to step 460 described above. FIG. 8A is one embodimentof a guidewire gauge 600 for guiding reaming depth of a glenoid. Gauge600 includes a proximal portion 610, a distal portion 620 and aplurality of depth markings along the length of the gauge adjacent theproximal and distal portions. During first step 400, in which apatient's anatomy is scanned, and the subsequent step 410, in whichfirst and second patient-specific guides 100, 300 are designed, softwarewill also assess cortical thickness of glenoid 8, namely the glenoidface. Upon analysis of the cortical thickness, a recommended reamingdepth that optimizes cortical thickness for a given baseplate curvaturewill be given. This allows for maximum placement and inhibitsover-reaming the glenoid in improper version.

FIGS. 8B and 8C show the guidewire gauge shown in FIG. 8A coupled toguides having a greater and lesser thickness, respectively. As shown inFIG. 8B, a guide having a greater thickness contacts glenoid 8 while atleast a portion of proximal portion 610 of gauge 600 is located adjacentcortical bone of glenoid 8. Gauge 600 is inserted into cortical boneuntil a depth “3” is adjacent an outer surface of the guide. As shown inFIG. 8C, a guide having a lesser thickness contacts glenoid 8 while atleast a portion of proximal portion 610 of gauge 600 is located adjacentcortical bone of glenoid 8. Gauge 600 is inserted into cortical boneuntil a depth “2” is adjacent an outer surface of the guide.

FIG. 8D is an exploded view of the scapula of FIG. 7A with a guidewiregauge 620 located in a marked position and a cannulated instrument 650having a reamer head portion 660 for preparing the glenoid. FIG. 8Eshows cannulated instrument 650 coupled to gauge 600 at depth “3”located at distal portion 620 of gauge 600. Because cannulatedinstrument 650 covers gauge 600 at proximal portion 610 thereof, thedepth markings located at distal portion 620 correlate to the depthmakings located at proximal portion 610 such that the user can visualizethe reaming depth during glenoid reaming.

FIGS. 9-10 refer to steps 480-530 described above. FIG. 9 depicts thescapula of FIG. 3 having baseplate 200 secured thereto via central screw280. FIG. 10 shows patient-specific guide 300 engaged to baseplate 200of FIG. 9B guiding peripheral screws 680 into baseplate 200 and into theresected glenoid 8 at a preoperatively planned trajectory. Guide 300functions to align two to four peripheral screws. With respect to thisfunction, guide 300 aligns with baseplate 200 and angles a drill to theoptimal trajectory for peripheral screws 680. A surgeon preferablydrills through guide 300, through baseplate 200, and into the glenoid 8for lateral peripheral screw 680 insertion. As shown in FIGS. 9-10,lateral boreholes 260 of baseplate 200 each have a central axis 290while peripheral screw holes 360 of guide 300 each have a central axis390. An angle θ is defined by the angle between central axis 290 andcentral axis 390 of corresponding lateral boreholes 260 and peripheralscrew holes 360, respectively. This angle is designed such eachperipheral screw 680 purchases optimal cortical bone according to thepreoperative plan.

FIGS. 11A-12D show a system of components for resecting a preoperativelyplanned depth D1 into bone. FIG. 11A shows guide 700 contacting asurface of scapular bone 2 in a preoperatively planned position. Guide700 has a patient-specific inner contact surface 720 and a bore hole740. Guide 700 further includes a base portion 730 and a shaft portion732. Cannulated portion or borehole 740 extends through the base portion730 and the shaft portion 732 and has a preoperatively planned lengthL1. Patient-specific inner contact surface 720 extends from base portion730 to a flange portion 734 such that contact surface 720 contacts theglenoid cavity as well as around and adjacent the scapular rim. Asdescribed above, the contact surface 720 is shaped based on preoperativeimage information such that guide 700 contacts bone 2 in only onepreoperatively planned position.

FIG. 11B is one embodiment of a guidewire gauge or marking pin 800 forguiding reaming depth of a glenoid. Gauge 800 includes a first portion810 having a first end 812 and a second portion 820 having a second end822. Gauge 800 further includes a plurality of depth markings 826 on anouter surface of gauge 800 along a length of gauge 800.

FIG. 11C is a perspective exploded view of a cannulated reamer 850having a shaft portion 860 and a reamer portion 870. Shaft portion 860has an internal guide portion 862 terminating at a stop surface 868, afirst end portion 864 and a second end portion 866. Reamer portion 870includes an outer reamer surface 872, a base surface 874 having a groove876 therein, and a cannulated portion or borehole 878 extending throughthe outer reamer surface 872 and base surface 874. Groove 876 ispreferably circular and is adapted to receive first end portion 864 ofshaft portion 860 in order to couple reamer portion 870 to shaft portion860 as shown in FIG. 12C. A linear reamer distance RD1 is defined by adistance between outer reamer surface 872 of reamer portion 870 adjacentthe cannulated portion 878 thereof and the stop surface 868 of theinternal guide portion 862 of the shaft portion 860.

In a method of resecting a preoperatively planned depth D1 into bone 2each of guide 700, marking pin 800 and cannulated reamer 850 are used.Software is used to assess cortical thickness of glenoid 8 of bone 2 anda desired amount of bone that should be resected in order to achieveproper glenoid baseplate location and orientation. The desired amount ofbone that will be resected during reaming is translated into reamingdepth D1. The analysis of the cortical thickness sets the recommendedreaming depth D1 that optimizes cortical thickness for a given baseplatecurvature. This allows for maximum placement of the baseplate andinhibits over-reaming the glenoid in improper version.

In one step of the method, patient-specific inner contact surface 720 isplaced against bone 2 in its preoperatively planned position. In anotherstep, a first end 812 of marking pin 800 is inserted into cannulatedportion 740 of guide 700 and into contact with the surface of bone 2.Marking pin 800 is then drilled into bone until a determined referencefeature or depth marking 826 on an outer surface of marking pin 800 liesadjacent a receiving end 742 of cannulated portion 740 of guide 700 asshown in FIG. 12A. The length of cannulated portion 740 is designed inorder to accurately position the marking pin 800 in bone 2 such that thecannulated reamer 850 resects a desired depth D1 into bone 2. Becausethe length of cannulated portion 740 is known, it can be preoperativelydetermined how deep marking pin 800 will be drilled into bone 2 based onthe location of a particular depth marking on the outer surface ofmarking pin 800 that will lie adjacent the receiving end 742 ofcannulated portion 740 of guide 700. Once the marking pin 800 is drilledin bone 2 a desired depth, guide 700 is removed leaving the marking pincoupled to bone 2 as shown in FIG. 12B. A linear marking distance MD1 isdefined by the distance between second end 822 of marking pin 800 and alocation of a desired reaming depth inside bone 2 along a longitudinalaxis 810 of marking pin 800. The linear reamer distance RD1 being atleast substantially the same as the linear marking distance MD1.

FIG. 12C is a plan view of marking pin or gauge 800 shown in FIG. 12B atleast partially housed within cannulated reamer 850 of FIG. 11C. Theadvancement of cannulated reamer 850 is guided by gauge 800 until gauge800 comes in contact with stop surface 868 such that it is fully seatedwithin cannulated reamer 850 as shown in FIG. 12D. Contact between gauge800 and stop surface 868 provides tactile indication that reaming iscompleted. Such contact may be visualized through a viewing window (notshown) in shaft portion 860 of cannulated reamer 850. Once gauge 800 isfully seated in cannulated reamer 850, the preoperatively planned depthD1 into bone 2 has been achieved. The amount of bone resected depends onthe angle the gauge 800 was inserted into bone 2 and also the topographyof the bone itself. Although outer reamer surface 872 has a curvaturepreferably substantially similar to that of a corresponding glenoidbaseplate surface, the amount of bone 2 resected along the outer reamersurface 872 may not be constant based on the topography of bone itself.

FIG. 13A-13C show another embodiment of a patient-specific guide 900engaged to native bone of a glenoid cavity and scapular bone. Guide 900has a patient-specific inner contact surface 920 and a bore hole 940.Guide 900 further includes a base portion 930 and a shaft portion 932.Cannulated portion or borehole 940 extends through the base portion 930and the shaft portion 932 and has a preoperatively planned length L2.Patient-specific inner contact surface 920 extends from base portion 930to a flange portion 934 such that contact surface 920 contacts theglenoid cavity as well as around and adjacent the scapular rim. Asdescribed above, the contact surface 920 is shaped based on preoperativeimage information such that guide 900 contacts bone 2 in only onepreoperatively planned position.

FIG. 13D is a plan view of cannulated portions 1040, 1140, 1240 and 1340of four patient-specific guides 1000, 1100, 1200 and 1300 respectivelyeach having a different lengths L3-L6. The length of these cannulatedportions is designed in order to accurately position a marking pin, suchas marking pin 800 into bone such that the a cannulated reamer, such ascunnulated reamer 850 resects a desired depth D1 into the bone. Becausethe lengths of the cannulated portions is known, it can bepreoperatively determined how deep marking pin 800 will be drilled intothe bone based on the location of a particular depth marking on theouter surface of marking pin 800 that will lie adjacent the receivingends 1042, 1142, 1242 and 1342 of cannulated portions 1040, 1140, 1240and 1340 respectively.

FIG. 14A shows another embodiment of a gauge 1500 prior to beingreceived in a cannulated portion 1440 of a patient-specific guide 1400.FIG. 14B shows gauge 1500 at least partially housed within cannulatedportion 1440 of patient-specific guide 1400, the cannulated portion 1440having a protrusion or grasping feature 1482 projecting outwardly froman inner wall surface 1480 of cannulated portion 1440. Cannulatedportion 1440 of guide 1400 has a receiving end 1464 and an exiting end1466, the internal wall surface 1480 adjacent receiving end 1464 ofcannulated portion 1440 having the protrusion or grasping feature 1482extending outwardly therefrom. The plurality of reference features 1526in an outer surface 1528 of marking pin or gauge 1500 are indentationssuch that when the gauge 1500 is received in receiving end 1464 ofcannulated portion 1440 of guide 1400 and translates with respect tocannulated portion 1440 until the grasping feature 1526 engages theindentation to inhibit the translation of the gauge 1500 with respect tocannulated portion 1440.

FIG. 15A shows another embodiment of a guidewire gauge 1700 with anotherembodiment of a patient-specific guide 1600 in phantom lines where alinear marking distance MD1 is measured from an end of gauge 1700 to anadir point 1710 along a surface of a desired resection line in theglenoid cavity. FIG. 15B shows gauge 1700 fully seated within acannulated reamer 1800 where a linear marking distance MD1 is measuredfrom a stop surface 1868 at an end of the cannulation of cannulatedreamer 1800 to an apex point 1872 of the reamer portion 1870 of thecannulated reamer 1800. The linear reamer distance RD1 being at leastsubstantially the same as the linear marking distance MD1.

FIG. 16 shows another embodiment of a marking pin or guidewire gauge800′. Gauge 800′ includes a first portion 810′ having a first end 812′and a second portion 820′ having a second end 822′. Gauge 800′ furtherincludes a plurality of depth markings 826′ on an outer surface of gauge800′ along a length of gauge 800′. The depth marking 826′ are shown asmeasurement lines on the outer surface of gauge 800′. For example, thenumerals “24,” “28,” “32,” and “36” each refer to appropriate depth toallow proper insertion depth as well as built-in reaming depth wheninserted to proper setting. These notches or lines represent appropriatesetting distance given reamer depth and size of center screw that willbe used to fix a glenoid baseplate to the resected glenoid cavity.

Although the invention herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent invention. It is therefore to be understood that numerousmodifications may be made to the illustrative embodiments and that otherarrangements may be devised without departing from the spirit and scopeof the present invention as defined by the appended claims.

1. A system for resecting a preoperatively planned depth into bonecomprising: a guide having a patient specific contact surface thatcontacts a surface of the bone in a preoperatively planned position, theguide having a cannulated portion including a length; and a marking pinhaving first and second ends, the first end adapted to be drilled intothe bone, the marking pin having at least one reference feature on anouter surface thereof, wherein the length of the cannulated portion ofthe guide is based on a location of the at least one reference featureon the outer surface of the marking pin.
 2. The system of claim 1further comprising: a cannulated reamer having a shaft portion coupledto a reamer portion.
 3. The system of claim 2, wherein the shaft portionhas an internal guide portion and the reamer portion includes a centralaperture, the marking pin being adapted to be inserted through thecentral aperture and into the internal guide portion.
 4. The system ofclaim 3, wherein the internal guide portion includes a stop surface. 5.The system of claim 4, wherein a linear reamer distance is defined by adistance between an outer surface of the reamer portion adjacent thecentral aperture thereof and the stop surface of the guide portion ofthe shaft portion.
 6. The system of claim 5, wherein when the markingpin is drilled into the bone a linear marking distance is defined by thedistance between the second end of the marking pin and a location of adesired reaming depth inside the bone.
 7. The system of claim 6, whereinthe linear reamer distance is substantially the same as the linearmarking distance.
 8. The system of claim 6, wherein a linear resectiondepth is defined by the distance between the surface of the bone priorto resection and the location of the desired reaming depth inside thebone.
 9. The system of claim 1, wherein the cannulated portion of theguide forms an internal wall having a receiving end and an exiting end,the internal wall adjacent the receiving end of the cannulated portionhaving a protrusion extending outwardly therefrom.
 10. The system ofclaim 9, wherein the at least one reference feature on the outer surfaceof the marking pin is an indentation such that when the marking pin isreceived in the receiving end of the cannulated portion of the guide andtranslates with respect to the cannulated portion until the protrusionengages the indentation to inhibit the translation of the marking pinwith respect to the cannulated portion.
 11. A method of resecting apreoperatively planned depth into bone comprising: contacting a surfaceof the bone in a preoperatively planned position with a guide having apatient specific contact surface, the guide having a cannulated portionincluding a length; inserting a first end of a marking pin into thecannulated portion of the guide and into contact with the surface of thebone, the marking pin having at least one reference feature on an outersurface thereof; and drilling at least a portion of the marking pin intothe bone until the at least one reference feature on the outer surfaceof the marking pin lies adjacent a receiving end of the cannulatedportion of the guide.
 12. The method of claim 11, further comprising:removing the guide from the marking pin; and inserting the marking pininto a cannulated reamer.
 13. The method of claim 12, furthercomprising: reaming the bone with the cannulated reamer until a secondend of the marking pin contacts a stop surface of an internal guideportion of the cannulated reamer.
 14. The method of claim 13, whereinthe cannulated reamer has a shaft portion coupled to a reamer portion,the shaft portion including the internal guide portion and the reamerportion including a central aperture, the marking pin inserted throughthe central aperture and into the internal guide portion.
 15. The methodof claim 14, wherein a linear reamer distance is defined by a distancebetween an outer surface of the reamer portion adjacent the centralaperture thereof and the stop surface of the guide portion of the shaftportion.
 16. The method of claim 15, wherein when the marking pin isdrilled into the bone a linear marking distance is defined by thedistance between the second end of the marking pin and a location of adesired reaming depth inside the bone.
 17. The method of claim 16,wherein the linear reamer distance is substantially the same as thelinear marking distance.
 18. The method of claim 16, wherein a linearresection depth is defined by the distance between the surface of thebone prior to resection and the location of the desired reaming depthinside the bone.
 19. The method of claim 11, wherein the length of thecannulated portion of the guide is based on a location of the at leastone reference feature on the outer surface of the marking pin.